The present invention relates to the field of cardiac stimulation, and more specifically to the field of stimulating cardiac tissue using a medical electrical lead.
Atrial arrhythmias and supra ventricular tachycardias, such as atrial fibrillation, atrial flutter and atrio-ventricular re-entry, are common post-operative complications among heart surgery patients. It is estimated that during the first seven to ten days after cardiac surgery post-operative supra ventricular tachycardia occurs in up to 63 percent of patients. Aranki et al. showed that patients with postoperative atrial fibrillation have a mean hospital stay of about fifteen days, whereas those patients without post-operative atrial fibrillation have a mean hospital stay of about ten days. Whether such extended hospitalization stays are primarily caused by arrhythmias is not known. See Cardiac Surg. Kirklin J W, Barrat-Boyes BC (Eds.): NY 1993, pg. 210, xe2x80x9cThe Importance of Age as a Predicator of Atrial Fibrillation and Flutter after Coronary Artery Bypass Graftingxe2x80x9d, Leitch et al., J. Thorac. Cardiovasc. Surg., 1990:100:338-42; xe2x80x9cAtrial Activity During Cardioplegia and Postoperative Arrhythmiasxe2x80x9d, Mullen et al., J. Thorac. Cardiovasc. Surg., 1987:94:558-65.
The presence of such arrhythmias, which in otherwise healthy patients may not be unduly serious, may be especially harmful to heart surgery patients. The surgery itself, the effects of prolonged anesthesia, or both have often already compromised the hemodynamic condition of such patients. Drugs that might be used to prevent post-operative atrial fibrillation are often only partially effective and may have negative effects on cardiac pump function.
Supra ventricular tachycardias may further cause a very irregular ventricular rate, which in turn can lead to hemodynamic conditions deteriorating even further. Such deterioration is especially serious for patients having a compromised left ventricular function. Such complications may also present a serious impediment to the recovery of the patient. See, for example, xe2x80x9cMaintenance of Exercise Stroke Volume During Ventricular Versus Atrial Synchronous Pacing: Role of Contractilityxe2x80x9d, Ausubel et al., Circ., 1985:72(5):1037-43; xe2x80x9cBasic Physiological Studies on Cardiac Pacing with Special Reference to the Optimal Mode and Rate After Cardiac Surgeryxe2x80x9d, Baller et al., Thorac. Cardiovasc. Surg., 1981:29:168-73.
If post-operative atrial fibrillation proves to have unacceptable hemodynamic consequences or causes serious symptoms, and if it does not stop spontaneously or antiarrhythmic drugs are ineffective in treating it, external cardioversion or atrial defibrillation may be required. But external atrial defibrillation, although generally effective as a treatment, may have profound side effects. First, and in contrast to ventricular defibrillation where conversion to normal sinus rhythm may occur after the first shock, atrial defibrillation may not be obtained until after several shocks have been delivered to the patient. This is because ventricular contraction continues during supra ventricular tachycardia. Due to the large amounts of energy, which must be delivered in external defibrillation (e.g., 40 to 360 Joules), the shocks are not tolerated well by conscious patients. External defibrillation is therefore preferably performed under general anesthesia or at least when the patient is sedated. The use of anesthesia gives rise to yet another patient risk factor.
External defibrillation requires relatively high energy because the electrical source is not positioned directly upon the cardiac tissue and instead must pass through the thorax, which tends to dissipate the energy. In contrast, internally applied atrial defibrillation, such as may occur during surgery through defibrillation paddles placed directly on the heart, requires considerably less energy because the defibrillation electrical energy is applied only to the tissue that needs to be defibrillated. In fact, direct atrial defibrillation may be accomplished with only one-Joule pulses in contrast to the 40 Joule and greater pulses required for external defibrillation. See, for example, Kean D., NASPE abs. 246, PACE, April 1992, pt. II, pg. 570.
Defibrillation success rates generally depend on the amount of energy delivered. The lower amount of energy delivered, the lower the defibrillation success rate and the greater the number of shocks that must be applied to obtain successful defibrillation. By way of contrast, in direct atrial defibrillation, where energy is applied directly to the heart, the energy level can be selected such that the patient may more easily tolerate both the amount of energy delivered as well as the number of shocks required.
Waldo et al. in xe2x80x9cUse of Temporarily Place Epicardial Atrial Wire Electrodes For The Diagnosis and Treatment of Cardiac Arrhythmias Following Open-Heart Surgery,xe2x80x9d J. Thorac. Cardiovasc. Surg., 1978, vol. 76, no. 4, pp. 558-65 disclose the use of a pair of temporary heart wires placed on the atrium to diagnose and treat arrhythmias through anti-tachycardia overdrive pacing. Temporary heart wires were sutured to the atrial walls at the time of the heart surgery. Once the patient was ready to be released from hospital, the wires were removed by traction or pulling upon the external end. See, for example, the temporary medical lead disclosed in U.S. Pat. No. 5,527,358 entitled xe2x80x9cTemporary Medical Electrical Leadxe2x80x9d to Mehmanesh et al.
Immobilization of mounting pads for electrical leads on the epicardium is currently accomplished by suturing the pad to the tissue, a potentially time-consuming process which can also cause damage to the patient""s myocardial tissue. Moreover, when the electrode of a lead is removed, the sutures and mounting pad remain within the patient, or must be removed from the patient. When non-biodegradable pads or sutures are employed, a foreign body response is typically elicited from the patient""s immune system. Such a response typically leads to scar tissue embedding the implanted electrode mounting pad or other components. The scar tissue may affect the performance of the patient""s myocardial tissue. Thus, there exists a need to provide an improved temporary medical lead which may be attached to and removed from a patient""s epicardium more quickly, which may be attached to and removed from the epicardium with less trauma occurring to a patient""s cardiac tissue, and which provokes a less severe response form the human body.
Various devices, compositions and methods relating peripherally or directly to the present invention are described in the patents and technical papers listed in Tables 1 and 2 below.
All patents and technical papers listed in Tables 1 and 2 hereinabove are hereby incorporated by reference herein, each in its respective entirety. As those of ordinary skill in the art will appreciate readily upon reading the Summary of the Invention, Detailed Description of the Preferred Embodiments and Claims set forth below, at least some of the devices and methods disclosed in the patents of Tables 1 and 2 may be modified advantageously in accordance with the teachings of the present invention. The foregoing and other objects, features and advantages, which will now become more readily apparent by referring to the following specification, drawings and claims, are provided by the various embodiments of the present invention.
The present invention has certain objects. That is, various embodiments of the present invention provide solutions to one or more problems existing in the prior art respecting conventional implantable pacing and/or defibrillation leads, including one or more of: (a) electrode mounting pad suturing times being excessive; (b) electrode mounting pad suture removal times being excessive; (c) damage or trauma occurring to a patient""s myocardium, epicardium or pericardium as a result of attaching an electrode mounting pad to a patient""s heart; (d) damage or trauma occurring to a patient""s myocardium, epicardium or pericardium as a result of removing an electrode mounting pad from a patient""s heart; (e) the requirement that a patient have an electrode mounting pad and corresponding medical lead surgically removed from within the patient""s body after the lead and pad have served their purpose; (f) the cost, pain, time and trouble associated with removing a medical lead from within a patient""s body.
Various embodiments of the present invention have certain advantages, including one or more of: (a) permitting lower defibrillation energy levels to be employed; (b) permitting fewer defibrillation pulses to be employed; (c) permitting temporary medical lead implantation surgical procedures to be completed more quickly; (d) reducing trauma or damage to a patient""s pericardium, myocardium or epicardium; (e) improved physical and electrical coupling of the electrode mounting pad to a patient""s pericardium, myocardium or epicardium; (f) eliminating the requirement that a patient have an electrode mounting pad and corresponding medical lead surgically removed from within the patient""s body after the lead and pad have served their purpose; (g) eliminating the cost, pain, time and trouble associated with removing a medical lead from within a patient""s body, and (h) being autologous.
Various embodiments of the present invention have certain features, including one or more of: (a) a collagen electrode mounting pad having a biodegradable adhesive attached thereto or loaded in at least portions thereof; (b) a biodegradable electrode mounting pad having a biodegradable adhesive attached thereto or loaded in at least portions thereof; (c) a non-biodegradable electrode mounting pad having a biodegradable adhesive attached thereto or loaded in at least portions thereof; (d) a method of making a biodegradable adhesive-loaded collagen electrode mounting pad and associated electrode; (e) a method of making a biodegradable adhesive-loaded biodegradable electrode mounting pad and associated electrode (f) a method of making a biodegradable adhesive-loaded non-biodegradable electrode mounting pad and associated electrode; (g) a collagen, biodegradable or non-biodegradable electrode mounting pad having a biodegradable adhesive attached thereto or loaded in at least portions thereof, where the adhesive dissolves and disappears within a patient""s body after a pre-determined post-operative period of time has elapsed sufficient to permit the electrical stimulating function of the pad to have been performed; (h) a collagen or biodegradable electrode mounting pad having a biodegradable adhesive having a biodegradable adhesive attached thereto or loaded in at least portions thereof, where both the adhesive and the pad dissolve and disappear within a patient""s body after a pre-determined post-operative period of time has elapsed sufficient to permit the electrical stimulating function of the pad to have been performed; (i) an electrode mounting pad having a biodegradable adhesive attached thereto or loaded in at least portions thereof which provides an improved degree of physical and electrical coupling of the pad to a patient""s heart, and (j) a collagen, biodegradable or non-biodegradable electrode mounting pad having a biodegradable adhesive attached thereto or loaded in at least portions thereof, where the adhesive is autologous.